1. Field of the Invention
The present invention relates to a hand-held percussion power tool, in particular to a hand-held chisel hammer and, more specifically, to a vibration-decoupling arrangement for supporting a percussion unit in the tool housing.
2. Description of the Prior Art
In hand-held percussion power tools, it is very important to be able to isolate the axial percussion load applied to the tool from the tool housing. In particular, in high-power hand-held power tools with power above 1,000 W, the percussion mechanisms have an axial percussion path in a range of several mm. In such tools, dependent on a different spatial orientation of a tool in space in accordance with the direction in which the work is effected, it is important to provide for a different preload of the percussion mechanism in the tool housing, using the gravity force.
European Publication EP 837756 discloses a hand-held percussion power tool in which the percussion unit is preloaded against the housing exclusively by a flexural parallelogram joint formed of leaf springs. The strong leaf spring, which are required for limiting the axial position of the percussion unit at a different spatial work orientation in a space, transmit strong vibrations to different points of the housing, inducing harmful additional lateral oscillating torques.
German Publication DE 2820125 discloses a hand-held power tool in which the percussion mechanism is supported against the tool housing by an axially extending, spiral compression spring.
German Publication De 3405922 discloses a hand-held power tool in which the percussion unit is supported against the housing by an axially extending helical compression spring and with a possibility of axial displacement which is limited by rubber rings.
U.S. Pat. No. 5,025,870 discloses a percussion hand-held power tool with a vibration-decoupled housing and including a parallelogram joint formed of two axially spaced articulated arms supported in slide bearings with a possibility of a limited pivotal movement, and a helical compression spring extending at an angle to the housing axis and preloaded against oscillation center in the housing, whereby lateral oscillation torques are prevented. However, the slide bearings of the tool have a high wear because of usual dust accumulation.
Accordingly, an object to the present invention is to provide substantially wear-free vibration-decoupled percussion unit for a percussion hand-held power tool.